Which of the following best describes magnetic fields? a. magnetic fields need a conductor. b. magnetic fields are always found in insulators. c. magnetic fields have north and south magnetic poles. d. magnetic fields must have only positive charges.

If you quadruple the temperature of a black body, by what factor will the total energy radiated per second per square meter increase? 1,024 64 16 4 256 submit answer

As a car drives with its tires rolling freely without any slippage, the type of friction acting between the tires and the road is 100) a) static friction. b) kinetic friction. c) a combination of static and kinetic friction. d) neither static nor kinetic friction, but some other type of friction. e) it is impossible to tell what type of friction acts in this situation.

Critical mass is the of material required to produce a chain reaction. a.) minimum amount b.) atomic mass c.) precise amount d.) maximum amount